I might just finish up the face of the cover by rubbing on a piece of fine wet & dry paper glued to a sheet of plate glass.
Well, that's what I did:
Then, had a go at removing the worst scratches on the 'public' side:
Just some rubbing with wet or dry paper then cloth and Solvol Autosol. Other metal polishes are available. Yesterday the filter cover drew blood, so while I was at it took a file to the rough edges near the screw holes.
Obviously not trying to reach XSive standards, but it's good enough to keep me happy.